Add the Model Context Protocol Server integration (#134122)

* Add the Model Context Protocol Server integration

* Remove unusued code in init

* Fix comment wording

* Use util.uild for unique ids

* Set config entry title to the LLM API name

* Extract an SSE parser and update comments

* Update comments and defend against already closed sessions

* Shorten description

* Update homeassistant/components/mcp_server/__init__.py

Co-authored-by: Paulus Schoutsen <paulus@home-assistant.io>

* Change integration type to service

---------

Co-authored-by: Paulus Schoutsen <paulus@home-assistant.io>